Hello again y’all. I made a post I wanna say about a year ago express some of my concerns and ideas of being a new h3 owner. I’ve come back with an important and dire question. The coolant leak in my h3 is significantly worse and has been overheating much more often. The reservoir gets sucked dry when I put new coolant in there and I’m constantly having to top off my radiator just to make sure the damned thing doesn’t blow up. Back when I first noticed something was up with the coolant, there was no visible leaks to where it would hit the pavement. As of about yesterday, I can see it dripping down from somewhere above the transmission, I wanna say right about behind the engine block. It’s not a steady leak more just a drip. The worst part is it’s not constant, it’s very on and off. My only theory is heat expansion is causing it to leak (specifically during the afternoon where it’s significantly hotter than the cool October mornings) My question to y’all is does anybody know of any common failure points for coolant to leaking from this area. Me and my father’s best guesses are the freeze plug but we’re not too sure. The biggest problem is that it’s somewhere that seems completely unreachable from a home garage standpoint, it seems like we’d have to drop the transmission or remove the engine to work on this. I can possibly attach a video I took of the leak to see if any of you smarter than me in hummer mechanics can help me out. I appreciate the help anyone will give me for I am at an impasse.

 

Year and Miles?

Freeze plugs are not a common source of coolant leaks.

Leak finding 101: Clean the engine and trans area with degreaser and rinse (repeat if necessary), let dry. Remove splash guard/skid plates. Next, start it and get under with bright lights and LOOK for the source of any leak. It is going to have to reach full operating temp so let it idle, or even take it for a short drive to let that happen before you get under and start looking.

Common coolant leaks with the H3 are almost always the Radiator, which if small enough, as you drive get blown back and may drip from the back of the engine, trans cross member, back of the splash guard(s), etc...
Water pumps also leak when they are worn out...... that is why Miles are important with every question?
Last, heater hose and/or connections can leak, they are at the firewall passenger side next to back of engine.

 

Also forgot to mention, check your Transmission fluid for contamination with coolant. If the Trans cooler loop inside your radiator is leaking fluid into the trans it can get cooked off out the Trans vent and kill the Trans as well.

 

 

Radiator coolant test dye is your best friend here.

 

We are desperate to get a report back on what you found and how you are addressing that. OK, so maybe not desperate, but at least interested....